The present invention relates to golf clubs and more particularly to putters. Superior putters are characterized by repeatable accurate sighting or aim, good forgiving performance on miss-hits, and a solid feel communicated to the hands upon impact with a golf ball.
Historically, most putters, being of the blade type, derived from irons, require the player to draw or imagine an aim line to the target, through the ball at right angles to the putterface. Some putters, especially mallet types, have one or more relatively short axially oriented (target line) Sight Lines, but they are visually overwhelmed by the larger transverse oriented putterface and the transverse putterhead lines. Axial sighting or aim is also effectively blocked by the golf ball in front of the putterface.
Forgiving performance is a major objective of most modern putter designers, especially those targeting non-professional players. Even if a clubhead is delivered square to the target line at impact, a golf ball will lose both distance and accuracy (i.e., go off line) if the ball is not struck precisely on an axis in front of the putter planar center of mass. The degree of distance loss and mis-direction from a particular miss-hit is directly related to the putter planar moment of inertia (“MOIP”). This is determined by the clubhead or putterhead planar moment of inertia (“MOICH”) and the position of the shaft in the putterhead which shaft weight and the shaft's own axial moment of inertia (“MOI”) contributes to the putter MOI. The higher the MOIP, the less the distance loss and angular misdirection for a given miss-hit. Putters typically have 9 to 18 cm facewidths with head weights of 280 to 350 gms and have MOIP of 2000–8000 gm cm2. (Long shafted putters are heavier). Putters typically produce 2% to 8% of distance loss with a 1 cm toe or heel miss-hit.
“Solid feel” is a more subjective term, but most golfers agree, undamped vibrations from center hits (on center of mass line) are helpful in establishing a feel for putt distance vs. putterhead striking velocity. Excessive strike face, or other putterhead interval vibration, is undesirable for putters and other clubs, and is traditionally eliminated through clubhead geometry (thick strike faces reinforced with bottom flanges or solid mallet type bodies). Harsh torsional vibrations from miss-hit putts are undesirable and can be reduced by increasing putter MOI or vibration dampening elastomers in or behind the strike face.
Toe-heel weighted putters (transverse bi-polar weighted) are the most popular type in current use, largely replacing traditional “blade” styles. Extreme bi-polar weighting such as that by Finney (U.S. Pat. No. 4,898,387), McGeeney (U.S. Pat. No. 5,938,543), Long (U.S. Pat. No. 4,693,478), and Duclos (U.S. Pat. No. 4,508,350), have produced designs with MOIP up to 8300 gm-cm2 for conventional sized putters (less than 13 cm facewidth and about 320 gms head weight). They are typically characterized by short or no axial alignment features. Sighting Fields are defined herein as axially oriented, usually light, bright, or white colored, areas roughly the width of a golf ball, on top of a putter which reduce the visual blocking effect on aim of a ball in front of a putterface. Sight Lines herein refer to axial lines, dots or points on top of a putter through the intended strikepoint or parallel to it and normal to the strikeface, to assist or facilitate axial (ball to target) “aim” or “sighting.” Axial bi-polar weighted (fore and aft weighted) designs (i.e. Winchall U.S. Pat. No. 5,080,365, and Pelz U.S. Pat. No. 4,754,976) have better sighting characteristics, but no better MOICH because a 13 cm putterhead width must have 13 cm or less of depth to conform to current USGA Rules.
FIGS. 1–4 compare prior art idealized theoretical maximum MOICH for transverse bi-polar or toe-heel weighted (FIG. 1) axial bi-polar (FIG. 2), and the present invention (FIGS. 3 and 4). All four theoretical putterheads have a 12.7 cm (5 in.) facewidth, weigh 300 gms (with weightless frames) and are USGA conforming dimensionally. The maximum theoretical planar MOICH for each using MOICH (I)=Mass (M)×(radius of gyration (r))2 is:                a. Transverse Bi-polar (FIG. 1) 12097 g-cm2         b. Axial Bi-polar (FIG. 2) 12097 g-cm2         c. Present invention tri-polar Mass Ring (FIG. 3) 18901 g-cm2         d. Present invention Multi-polar Mass Ring (FIG. 4) 23710 g-cm2         
In preferred embodiments of the present invention, putter moment of inertia (MOIP) exceeds the MOICH values above because the shaft axis is substantially forward of the center of mass.
Putters with elongated (over 75% of facewidth) axial Sighting Fields or Sight Lines are less common, but do exist. Current examples include, Callaway's White Hot “2-Ball” putter, Golf Digest, 3–02, Pg. 159 (a derivative of Pelz U.S. Pat. No. 4,754,976), as well as, Winchall U.S. Pat. No. 5,080,365, and other T-shaped putters cited (Klein U.S. Pat. No. 5,072,941, Panlin U.S. Pat. No. 4,141,556, Dalton U.S. Pat. No. 4,138,117, Bendo U.S. Pat. No. 5,470,070, Lin U.S. Pat. No. 5,795,239, Jenkins U.S. Pat. No. 6,045,453, Whitney D U.S. Pat. No. 323,688, Lannoch D U.S. Pat. No. 422,328). None of these maximizes either MOICH or MOIP. The present invention maximizes both. Most of these utilize a “Sight Line” (an elongated line less than 1 cm wide through the intended strike point). Few (only Pelz and Klein) use an axial Sighting Field (but no Sight Line). Again, only the present invention combines a Sighting Field with maximum MOICH and MOIP. Only one Sight Field putter (U.S. Pat. No. 4,962,293 to Jazdzyk) other than the present invention attempts to take all components outside the Sighting Field or Sight Line out of planar view, but this design does not address MOI and uses a transparent/translucent putterhead material, thus not conforming to USGA rulings. The present invention uses a high open area rigid putterhead frame and dark non-reflective planar coloration outside the Sighting Field or Sight Line.